This invention relates to dunnage for use in shipment of freight by rail, ship, truck, aircraft, and the like, and more particularly, to an inflatable, disposable dunnage bag for such use. Typically, such dunnage bags have a gastight bladder (usually polyethylene) surrounded by an outer protective and supportive shroud consisting of a number of plies of heavy paper.
The inflatable, disposable dunnage bags are used in freight carriers where it is customary to fill the spaces between the cargo or between the cargo and walls of the freight carrier to prevent the cargo from shifting and damaging either the cargo itself and/or the walls of the freight carrier. Inflatable disposable dunnage bags are placed between the cargo in a deflated condition and are subsequently inflated with high pressure air to a certain design pressure, usually between one and eight pounds per square inch, depending on the size and wall structure of the particular bag.
Experience with this type of dunnage bag has revealed certain difficulties during inflation. First, the bags are normally inflated with high pressure air nozzles through a valve in the side of the bag. When the bag is placed up against or between cargo, the air nozzle, when placed over the bag valve and pressed thereagainst, forces the valve into the wall of the bag opposite the valve and against the cargo. This tends to block the discharge area of the valve inside the dunnage bag and tends to prevent the high pressure air from flowing through the valve and into the bag. Consequently, a person who is filling such a dunnage bag under these circumstances must take extra care and extra time to pull the bag valve away from the back wall of the dunnage bag as the bag is being inflated.
Secondly, it has been found that as pressurized air is introduced through the valve, a portion of the wall of the bladder opposite the valve is subjected to a high pressure jet of inrushing pressurized air. This can cause a vibration of the bladder wall opposite the valve which seriously strains and weakens the bladder wall and sometimes causes the bladder wall to fail or rupture.
Third, when dunnage bags of this type are used in freight carriers subjected to high impact loading conditions (such as in railroad cars when the cars are being "bumped"), the plug member inside the valve can be blown out of engagement with the valve housing during peak pressure transients generated within the bag by the impact.
Attempts have been made to solve some of the above described problems. For example, many dunnage bags today are provided with handles near the valve so that the valve can be pulled away from the opposite wall of the dunnage bag during filling to allow the air to pass through the valve and into the bag. Nevertheless, this requires that the person filling the dunnage bag grasp the handle and pull the valve outwardly away from the opposite wall of the bag. Further, in many situations, there is not enough room between the cargo to allow the valve to be pulled sufficiently far away from the other wall of the bag.
There have been many attempts to solve the problem of bladder rupture during inflation of the dunnage bag with high pressure. Examples of such attempts are the structures disclosed and claimed in the U.S. Pat. to Feldkamp, No. 3,414,140; Shaw, No. 3,808,981; Baxter, No., 3,868,026; Reeves, No. 3,944,084; and Reeves, No. 3,960,281. Though some of these attempts may have succeeded in eliminating the bladder rupture problem, all of the attempts nevertheless increase the complexity and costs of the bag by requiring additional members, structures, housings or material to be incorporated in the dunnage bag. Further, these attempts do not address the other two problems.
It would be desirable to provide a dunnage bag having a simple and inexpensive design which, through one simple mechanism, solves the above described three problems.